West Lake Sammamish climate — normals and trends
West Lake Sammamish (United States) has a warm-summer mediterranean climate (Csb) under the Köppen-Geiger classification. Its mean annual temperature is 9.8 °C and it receives 1,670 mm of precipitation per year.
These figures are normals computed over 86 complete calendar years, from 1940 to 2025, using ERA5 reanalysis data from the Copernicus programme.
The warmest month is July (17.5 °C on average) and the coldest is January (3.2 °C). Rainfall peaks in November.
West Lake Sammamish averages 47 frost days, 6 hot days (≥ 30 °C) and 172 rainy days per year.
West Lake Sammamish has warmed by +1.5 °C between 1940 and 2025, or +0.18 °C per decade. This trend is statistically significant.
The number of frost days there went from about 61 to 33 per year over the period.
The hottest day of the period reached 42.2 °C (on 28 June 2021) and the coldest -20.8 °C (on 9 January 1949).
Data from ERA5 reanalysis (Copernicus Climate Change Service), redistributed under a CC-BY 4.0 licence. Normals are recomputed whenever the archive is updated.
Climate normals · ERA5
West Lake SammamishWashington
- coords
- 47.58°, -122.10°
- period
- 1940–2025 · 86 yrs
Mean daily temperature
9.8°C
Average daily high
14.4°C
Average daily low
5.8°C
Annual rainfall
1,670mm
Sunshine / day
8.2h
Mean relative humidity
78%
Average peak wind
12.4km/h
Seasonal range
14.3°C
Frost days (< 0 °C)
47 d/yr
Hot days (≥ 30 °C)
6 d/yr
Rainy days (≥ 1 mm)
172 d/yr
Annual snowfall
50.8 cm
Average feels-like high
12.8 °C
Average feels-like low
3.4 °C
Average peak gust
33.6 km/h
Tropical nights (≥ 20 °C)
0 d/yr
Solar radiation
12.4 MJ/m²
Has the climate changed?
One stripe per year, 1940 to 2025
+1.5 °C
since 1940
+0.2 °C per decade · r² = 0.37 · p = < 0.001
Trend fitted by linear regression (ordinary least squares) on annual means. A trend is shown only when it is statistically significant (p < 0.05).
A climograph overlays rainfall (bars) and temperature (line): the standard reading in climatology, where you can see at a glance whether the warm season is also the dry one.
Records for the period
Hottest day
42.2 °C
28 June 2021
Coldest day
-20.8 °C
9 January 1949
Wettest day
97 mm
24 November 1990
Windiest day
43.3 km/h
20 January 1993
Strongest gust
120.2 km/h
20 January 1993
Hottest feels-like
45.6 °C
28 June 2021
Coldest feels-like
-25.7 °C
9 January 1949
Snowiest day
30.0 cm
18 November 1946
Sunniest day
15.7 h
17 June 2025
Normals computed over complete calendar years 1940–2025.
A specific year
Pick a year and see how it compares to normal — warmer, drier or more extreme than usual?
Across the whole year
Month by month
| High | vs. normal | Precipitation | vs. normal | |
|---|---|---|---|---|
| Jan | 7.0 °C | +0.7 °C | 90 mm | -132 mm |
| Feb | 7.2 °C | -1.2 °C | 172 mm | +2 mm |
| Mar | 11.5 °C | +0.8 °C | 228 mm | +64 mm |
| Apr | 15.2 °C | +1.6 °C | 105 mm | -27 mm |
| May | 17.3 °C | +0.2 °C | 77 mm | -24 mm |
| Jun | 20.8 °C | +1.2 °C | 24 mm | -59 mm |
| Jul | 24.3 °C | +1.2 °C | 8 mm | -28 mm |
| Aug | 23.7 °C | +0.6 °C | 88 mm | +41 mm |
| Sep | 21.2 °C | +1.1 °C | 34 mm | -56 mm |
| Oct | 14.2 °C | -0.4 °C | 176 mm | +9 mm |
| Nov | 11.3 °C | +2.0 °C | 238 mm | +7 mm |
| Dec | 8.9 °C | +2.5 °C | 419 mm | +194 mm |
The year's extremes
What was the weather like that day?
Your birthday, a wedding, a memorable trip: discover the actual weather for any date since 1940.
Frequently asked questions
What is the climate of West Lake Sammamish?
West Lake Sammamish has a warm-summer mediterranean climate (Köppen Csb). Over 1940-2025, the average annual temperature is 9.8 °C and it receives 1,670 mm of precipitation per year.
What is the hottest day ever recorded in West Lake Sammamish?
The hottest day measured in West Lake Sammamish between 1940 and 2025 was 28 June 2021, reaching 42.2 °C.
What is the coldest day in West Lake Sammamish?
The coldest day measured in West Lake Sammamish between 1940 and 2025 was 9 January 1949, at -20.8 °C.
Does it snow in West Lake Sammamish?
Yes. West Lake Sammamish gets on average 50.8 cm of snow per year and has around 47 frost days.
Has the climate of West Lake Sammamish warmed?
Yes: West Lake Sammamish warmed by +1.5 °C between 1940 and 2025, a statistically significant trend.
What is the wettest day in West Lake Sammamish?
The wettest day measured in West Lake Sammamish between 1940 and 2025 was 24 November 1990, with 97 mm of rain in 24 hours.
What was the windiest day in West Lake Sammamish?
The windiest day measured in West Lake Sammamish between 1940 and 2025 was 20 January 1993, with winds reaching 43.3 km/h.
What is the warmest month in West Lake Sammamish?
The warmest month in West Lake Sammamish is July (17.5 °C on average); the coldest is January (3.2 °C).
How much does it rain in West Lake Sammamish?
West Lake Sammamish receives on average 1,670 mm of precipitation per year, spread over about 172 rainy days.
Is it sunny in West Lake Sammamish?
West Lake Sammamish gets on average 8.2 hours of sunshine per day, roughly 2,993 hours per year over 1940-2025.
What is the biggest single-day snowfall in West Lake Sammamish?
The heaviest 24-hour snowfall measured in West Lake Sammamish between 1940 and 2025 was 18 November 1946, with 30.0 cm.
Are there tropical nights in West Lake Sammamish?
Almost never: tropical nights (temperature staying above 20 °C) are virtually non-existent in West Lake Sammamish.
What was the most extreme apparent temperature in West Lake Sammamish?
In West Lake Sammamish, between 1940 and 2025, the highest apparent temperature reached 45.6 °C on 28 June 2021, and the lowest was -25.7 °C on 9 January 1949.
Compare West Lake Sammamish with another city
Pick a second city: its normals will be set against these, indicator by indicator.
Nearby cities
The climate around West Lake Sammamish